JPS59184324A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display element which is low in adhering temp., has adhesive power, is stable to contact with a liquid crystal and has excellent productivity and durability by using a specific urethane adhesive agent as a sealant. CONSTITUTION:A transparent electrode such as In2O3-SnO2 or the like is formed on the surface of a plastic film and if necessary an overcoating layer of a resin is further formed thereon. The film is then subjected to an orienting treatment such as rubbing or treatment with a vertical orienting material, thereby forming a substrate. The electrode of the rear side substrate is formed as a reflective electrode. An undercoating layer of SiO2, resin, etc. is formed between the plastic film and the electrode. The substrates formed in such a way are mated in such a way that the electrode surfaces face each other, then the periphery is sealed with a sealant. An urethane adhesive agent which brings a polyol compd. and an aliphat. isocyanate into reaction is used as the sealant. The sealant is mixed with a spacer material such as glass fibers, alumina particles or the like in order to regulate the cell spacing and is printed on the sealing part of the substrates by screen printing, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal display element using a plastic film as an electrode substrate, and particularly relates to a peripheral sealing material for encapsulating liquid crystal used in the manufacture of a liquid crystal display element. More specifically, the present invention relates to a urethane sealing material made by reacting an aliphatic isocyanate compound and a polyol compound.

Conventionally, a glass plate coated with indium oxide or tin oxide has been used as a transparent conductive substrate used in a liquid crystal display element, and a glass frit or epoxy adhesive, which has a high molding temperature, has been used as a sealing material. I've been exposed to it. However, in recent years, there has been a desire to realize a liquid crystal display element that is inexpensive, thin, and has flexo rigidity. That is, by reducing the thickness of the substrate, it becomes easier to reduce the thickness of the entire display device, and in the case of reflective elements, so-called double images are eliminated, so that the display contrast and viewing angle are improved.

In order to achieve this, it has been experimentally confirmed that it is desirable for the substrate thickness to be 200μ or less, but if such a thickness is to be achieved with a glass substrate, it has the drawbacks of high cost and frequent cracking during manufacturing or use. was there. In order to overcome these drawbacks, using a plastic film as a substrate is more advantageous and more practical than a glass substrate in terms of cost and flexibility. However, the conventionally used glass frit and epoxy sealants are
In addition to the adhesive temperature being too high, the adhesive strength to the film is poor.
It had the disadvantage that it peeled off easily.

The object of the present invention is to obtain a liquid crystal display element using a plastic film that eliminates such drawbacks. This is a liquid crystal display element characterized in that when a urethane adhesive formed by reacting a polyol compound and an isocyanate compound is used as a sealing material, an aliphatic incyanate is used as the incyanate compound.

The liquid crystal display element of the present invention has a low bonding temperature by using a specific urethane adhesive as its sealing material.
It has strong adhesive strength, does not easily peel off even when bent, has a pot life that can be used stably for a long time during mass production, and is stable even when in contact with liquid crystals, and has excellent productivity and durability. It is something.

Plastic films used in the present invention include transparent films such as polyester films, cellulose acetate films, polycarbonate films, and polyethersulfone films, and usually have a thickness of about 50 to 300 μm. Among these, polyester film is preferable in terms of optical performance, heat resistance, chemical resistance, etc., and is preferable because it has good adhesiveness with the polyurethane resin sealant of the present invention.

This type of plastic film has an engineered n2o3 surface.
A transparent electrode such as S n 02 is formed, a resin overcoat layer is further formed as required, and an alignment treatment is performed by rubbing or vertical alignment agent treatment to form a substrate. or,
The electrodes on the back substrate may be reflective electrodes, an undercoat layer of resin or the like may be formed between the plastic film and the electrodes, or the electrodes may be wired in two layers.

The periphery of the substrate manufactured in the same manner as above is sealed with a sealing material so that the electrode surfaces face each other.

In the present invention, a urethane adhesive made by reacting a polyol compound with an aliphatic incyanate is used as the sealing material, and is mixed with spacer materials such as glass fiber and alumina particles to define the cell gap. , it may be printed on the seal portion of the substrate by screen printing or the like.

Of course, in the case of a large display element, a seal portion may be formed inside in addition to the peripheral seal portion.

Further, spacer interest may be sprinkled on the display portion of the non-sealed portion.

In the present invention, since aliphatic isocyanate is used as the incyanate, there is no need for surface treatment with incyanate for the sealing part of the substrate, and the adhesive strength is much higher than when polyol and aromatic isocyanate are used. However, it has higher adhesive strength than when polyol and aromatic isocyanate are used after base treatment with aromatic incyanate. In particular, the material of the film has excellent adhesiveness with polyester film.

In the present invention, various additives other than polyol and aliphatic incyanate may be mixed. Specific examples include polyisocyanate, polyol, chain extender (crosslinking agent) as main raw materials, catalyst, blowing agent, There are products containing appropriate mixtures of foam stabilizers, flame retardants, fillers, etc.

Examples of the present invention will be shown below.

Example 1 As a polyol, a glyceride compound of carboxylic acid made of vegetable oil, a mixture of glycerin and propylene glycol, and hexamethylene diisocyanate (HD engineering)
A urethane adhesive containing 5% by weight of Aerosil is mixed with isocyanate having a buret type structure.
When screen printing was performed on a polycarbonate film, the average height of the printed seal was 10 to 14μ and the seal width was α5 to 0.65 for up to 5 hours after compounding.
The pot life was constant, and the printable time was 5 hours or more, which was sufficient for mass production. After printing further, 10
After precuring at 0°C for 50 minutes, the two films were superimposed and hot pressed at 100°C for 10 minutes, resulting in a seal height of 8 to 9μ and a seal width of Q, 8.
It was possible to seal with a good seal shape within the range of 5 to 1.05 degrees.

Furthermore, even after the cell thus produced was wrapped around a cylinder with a diameter of 60 strips and subjected to a repeated bending test 10,000 times, no peeling between the film and the sealing material was observed. The average adhesive strength of this adhesive to polyester and polyether sulfon films is as follows:
It was 320 f/cFn2 and 22097 cm2.

Example 2 As the incyanate of the adhesive shown in Example 1, (H
Even when a similar test was carried out using the trimmer mold of D), the printing and pressing conditions were stable to the same extent for 5 hours. Furthermore, in a bending test of 10,000 times, no peeling of the seal was observed in any of the films.

Example 3 Polyester, polyether sulfon film, ■
Coat To with a thickness of 300A by sputtering,
After baking, a polyamide resin was coated as an alignment film, a rubbing alignment treatment was performed, and using the adhesive shown in Examples 1 and 2, -7(
BDH Co., Ltd.) to make a TN type element, and heat it at 40°C.
A 500-hour humidity test was carried out at 90% RE, but the liquid crystal orientation did not change and it was stable.

Next, as a comparative example of the present invention, a case where an aromatic type is used as the incyanate of the urethane adhesive shown in Example 1 will be shown as a comparative example.

Comparative Example When a similar test was conducted using a polyol-modified product of crude MDI (diphenylmethane diisocyanate) as the isocyanate compound constituting the adhesive in Example 1, it was found that the sealing material was significantly cured 30 minutes after it had been prepared. This made printing and pressing impossible. Furthermore, when the adhesive strength to polyester and polyether sulfon was evaluated, the adhesive strength was 5o and 11°2/σ2, respectively, which was lower than in Example 2.

As is clear from the above examples, the sealing material according to the present invention has a low curing temperature, a long pot life, and high adhesive strength, so it has good bending durability and can be used under high temperature and high humidity conditions. It was also found that this sealant has no adverse effect on the alignment of liquid crystal molecules and is a highly stable sealing material.

In the examples, Aerosil is added to provide thixotropic properties in order to print the stickers continuously in a fixed shape, and in order to achieve this condition, other It may be an additive. Furthermore, the additive concentration must be selected based on the conditions that suit the equipment, and the equipment used.
The essential properties of the sealant may be changed depending on the requirements, and other additives such as barium sulfate, magnesium sulfate, glass fibers, spherical plastic particles, etc. may be added for viscosity adjustment, thickness control, etc. remains unchanged. Various types of polyols are known, and modified vegetable oils such as castor oil and linseed oil can be used, and these have the effect of imparting flexibility to the cured product. In addition, other polyols include polyether,
Polyester-based, polybutadiene-based, modified products thereof, etc. are used.

As for isocyanate compounds, aromatic and aliphatic ones have the advantage of lower reaction activity and longer pot life, and are advantageous for continuous use. Furthermore, among them, H
The buret type and trimmer type of the DI type are liquid at room temperature and can be mixed with polyol without being dissolved in a solvent, making them easy to use and suitable for solvent evaporation during continuous use. According to the invention, plastic tube ilm,
It is possible to bond polyester film, which is said to be particularly difficult to bond, without sacrificing the flexibility of plastic film, and has excellent weather resistance.
It is extremely excellent as a sealant for display elements.

In addition to this example, the present invention can be applied in various ways6')
, multilayer display elements using 6 or more substrates, display elements using polarizing plates as substrates, various types of printing on substrates, formation of single glare treatment layers, color filter lamination, use of color polarizing plates, etc. Various applications are possible. It is something.

Claims (1)

[Claims] 1) In a liquid crystal display element using a plastic film as a substrate, 3. As a peripheral sealing material for enclosing liquid crystal,
A liquid crystal display element characterized in that an aliphatic incyanate is used as the incyanate compound when using a urethane adhesive formed by reacting a polyol compound and an isocyanate compound. 2) A liquid crystal display device characterized in that a compound consisting of a hexamethylene diisocyanate derivative is used as the incyanate compound. 3) The liquid crystal display element according to claim 2, wherein a compound having a biuret type structure and a compound having a trimer type structure are used as the hexamethylene diisocyanate derivative.